What is encephalitis?
Encephalitis is inflammation of the brain. This inflammation can cause symptoms such as confusion, a fever, a bad headache, and a stiff neck. Sometimes it leads to symptoms like seizures and personality changes. It can also cause long-term problems, such as trouble with speech or memory.
Encephalitis is uncommon, but it can be deadly. If you think you have symptoms of encephalitis, see a doctor right away.
What causes it?
Infection with a virus is the main cause of encephalitis. Different types of viruses can cause the illness. For example, West Nile virus can cause encephalitis when a person is bitten by an infected mosquito. Another type is the herpes simplex virus, which is the same virus that causes cold sores and genital herpes. A mother who is infected with the herpes virus can also pass the virus to her baby. If this happens and the baby gets encephalitis, it is very serious.
Encephalitis also can be caused by bacteria or by a parasite, such as the one that causes toxoplasmosis. In rare cases, encephalitis can be caused by a fungus.
But most people who get these types of infections don't get encephalitis.
What are the symptoms?
Symptoms of encephalitis can include:
- A fever.
- A headache (which can be very painful).
- A stiff neck and back.
- Light hurting your eyes.
- Nausea and vomiting.
- Lack of energy.
More serious symptoms include:
- Personality changes.
- Memory loss.
- Hallucinations (seeing or hearing things that aren't there).
If you think that you or your child has encephalitis, call your doctor right away.
How is it diagnosed?
Your doctor will ask questions about your past health and your symptoms. He or she will likely order tests to confirm the diagnosis. These may include:
- Spinal fluid analysis.
By doing a lumbar puncture (also called a spinal tap), your doctor can check the spinal fluid for an increase in white blood cells and protein. The bacteria, virus, parasite, or fungus causing the encephalitis also may be found in the spinal fluid.
- Imaging tests.
- Electroencephalogram (EEG).
This test can measure the electrical signals in the brain. It may show a change related to the illness.
- Blood tests.
These tests can show what type of virus is causing encephalitis.
How is encephalitis treated?
If you have encephalitis, you will need to be treated in a hospital. Your treatment will depend on your symptoms and the cause of your illness. You may be treated right away with an antiviral medicine, such as acyclovir. Antiviral medicine may make symptoms less severe, especially if you get the medicine right away. If the doctor thinks that your symptoms are caused by bacteria, rather than by a virus, he or she may treat you with antibiotics.
You will also get care to ease your symptoms and allow your body to heal on its own. This is called supportive care. You may take medicines to reduce pain and fever or to stop seizures. In some cases, you may need a machine called a ventilator to help you breathe.
After you are out of the hospital, it may take several weeks, months, or even longer to fully recover from your symptoms. You can take care of yourself by eating well and getting plenty of rest. Follow your doctor's instructions on how much fluid to drink. If your doctor says it's okay, you can take nonprescription pain relievers for headaches. These include acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) like naproxen, ibuprofen, or aspirin. Do not give aspirin to anyone younger than 20 because of the risk of Reye syndrome. Be safe with medicines. Read and follow all instructions on the label.
Some people have long-term problems. If you have muscle weakness or problems with coordination, you may need physical therapy. If you have speech or memory loss, you may need speech therapy or occupational therapy.
How can you lower your risk?
Your chance of getting encephalitis is low. But there are things you can do to reduce your chances even more.
- Make sure that you and your children get vaccines against measles, mumps, rubella, chickenpox, and the flu.
- Avoid areas where there has been an outbreak of viral encephalitis. If you can't avoid these areas, prevent mosquito bites with these tips:
- Stay indoors at dawn, at dusk, and in the early evening, when mosquitoes are most active.
- Wear long-sleeved shirts and long pants whenever you are outdoors and are likely to be where mosquitoes are.
- Avoid wearing floral fragrances from perfumes, soaps, hair care products, and lotions. These may attract mosquitoes.
- Use insect repellent with DEET (N,N-diethyl-meta-toluamide). The repellent is available in varying strengths up to 100%. The American Academy of Pediatrics (AAP) and other experts suggest that it is safe to use a repellent that contains 10% to 30% DEET on children older than age 2 months.
- Spray clothing with an insect repellent containing permethrin or DEET, because mosquitoes may bite through thin clothing. DEET can damage plastic items, such as watch crystals or eyeglass frames, and some synthetic fabrics. You also can use natural products such as soybean-based Bite Blocker.
- Avoid applying repellent to the hands of children. Repellents may irritate the eyes and mouth.
- Whenever you use an insecticide or insect repellent, be sure to read and follow the directions for use.
- Do not keep open containers of water near your house. Standing water is a breeding place for mosquitoes.
- If you are taking a long trip to East Asia or to central or eastern Europe, talk to your doctor about getting vaccinated against certain types of mosquito- or tick-borne encephalitis. For example, there is a vaccine for Japanese encephalitis. Getting vaccinated is especially important if you are going to a rural area.
Current as of: July 1, 2021
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
Christine Hahn MD - Epidemiology